1. Field of the Invention
The present invention relate to a light emitting device driving circuit.
In recent years, along with the advances made in optical communications and the advances made in an optical disc device etc., use of light emitting devices has rapidly spread. Looking at the optical communications, for example, an optical repeater is one of the important devices for realizing optical communications. In this optical repeater, a semiconductor laser or other light emitting device is used. This plays the role of converting an input electrical signal to an optical signal.
The light emitting device driving circuit according to the present invention is a driving circuit particularly preferred for driving a light emitting device comprised of a semiconductor laser (laser diode).
2. Description of the Related Art
As will be explained in detail later by using the drawings, when a light emitting device having a threshold current (Ith) or a differential quantum efficiency (.eta.) which fluctuates according to the temperature is used as the above light emitting device, in the light emitting device driving circuit of the related art, the optical output power (Pout) fluctuates according to the fluctuation of the temperature. For this reason, when such a light emitting device is used in the light emitting device driving circuit of the related art, of course, there is a problem that the range of the operating temperature is limited, so application to a circuit where optimum operation is required in a wide range of temperature is difficult. Conversely, when it is desired to apply the light emitting device driving circuit of the related art to a circuit where optimum operation is required in a wide range of temperature, there arises a problem in that the selection of the light emitting device becomes difficult.